Production method for sustained-release preparation

ABSTRACT

This invention provides a production method for a solid sustained-release preparation, characterized in that a sustained-release preparation (a sustained-release preparation suspension) is freeze-dried in a freeze-drying container whose inner face is partially or totally coated with an ice layer or water-repelling base material.

TECHNICAL FIELD

The present invention relates to a production method for a solidsustained-release preparation such as in microsphere form that enableseasy recovery of the solid sustained-release preparation withoutenvironmental exposure for a long time.

BACKGROUND ART

A microcapsule (microsphere) (hereinafter also referred to as MC) isfirst prepared by the aqueous drying method etc., then separated,concentrated and recovered, after which mannitol etc. are added anddissolved, to yield an MC suspension, which is then dehydrated and driedby freeze-drying to yield a finished microcapsule powder (microspherepowder) (hereinafter also referred to as MC powder). In this operation,it is common practice to dispense the MC suspension to a tray andfreeze-dry the suspension.

However, because of the necessity of manual aseptic removal and recoveryof the MC powder from the tray using a scraper after completion offreeze-drying, the conventional method has the drawbacks describedbelow.

(1) MC powder adhesion to the tray necessitates the removal of MC powderusing a scraper at time of their recovery.

(2) Because scraping is conducted manually, and because relatively longtime is taken to recover the MC, the MC is exposed to the environmentfor an extended period of time, resulting in the constant risk ofcontamination with microorganisms etc., an aspect undesirable from theviewpoint of assurance of sterility. Also, because MC preparations needwater content control, such long environmental exposure pose a risk fromthe viewpoint of physicochemical stability.

(3) Because the use of a scraper is essential for the scraping process,there is a risk of production and invasion of foreign substancesattributable to friction between the tray and scraper.

(4) Because of adhesion of the MC powder and tray, some MC powdersremain on the tray and unrecovered, even after scraping.

DISCLOSURE OF INVENSION

Against this background there has been a demand for the development of aproduction method for a solid sustained-release preparation that enableseasy recovery of the solid sustained-release preparation afterfreeze-drying at high recovery rates, with short environmental exposuretime and reduced risk for production and entry of foreign substances.

After extensive investigation aiming at resolving the above problem, thepresent inventors have found that by previously forming an ice layer orcoating the inner face of the tray with a water-repelling base material,the freeze-dried MC powder can be recovered unexpectedly in a short timeand with ease. Further, the present inventors have found that bycompleting the sublimation of frozen water in the freeze-dryingcontainer under reduced condition that the temperature in thefreeze-drying container is 0° C. or below, the freeze-dried cake doesnot collapse or scatter, and consequently, the freeze-dried MC powdercan be recovered unexpectedly in a good form and high yield. Theinventors have conducted further investigation based on this finding,and developed the present invention.

Accordingly, the present invention provides:

-   (1) a method for producing a solid sustained-release preparation,    which comprises freeze-drying a sustained-release preparation in a    freeze-drying container of which the inner face is partially or    wholly coated with an ice layer or water-repelling base material,-   (2) a method for producing a solid sustained-release preparation,    which comprises freeze-drying a sustained-release preparation in a    freeze-drying container of which the inner face is partially or    wholly coated with a water-repelling base material, and the coated    inner face is further partially or wholly coated with an ice layer,-   (3) the method according to term (1) or (2) above wherein the inner    face is the bottom face alone,-   (4) the method according to term (1) or (2) above wherein the    freeze-drying container is a tray,-   (5) the method according to term (1) or (2) above wherein the ice    layer has a thickness of about 0.01 mm to about 30 mm,-   (6) the method according to term (1) or (2) above wherein the    water-repelling base material is ethylene tetrafluoride resin,    ethylene trifluoride resin, ethylene difluoride resin, vinylidene    fluoride resin, propylene hexafluoride-ethylene tetrafluoride    copolymer resin, modified fluorine resin, ethylene    tetrafluoride-perfluoroalkoxyethylene copolymer resin, or ethylene    tetrafluoride-ethylene copolymer resin,-   (7) the method according to any one of terms (1) through (6) above    wherein said sustained-release preparation is a microsphere, and-   (8) the method according to term (1) or (2) above which comprises    completing the sublimation of frozen water in the freeze-drying    container under reduced condition that the temperature in the    freeze-drying container is 0° C. or below,

The present invention further provides:

-   (9) the production method according to term (1) or (2) above wherein    the thickness of said ice layer is about {fraction (1/1,000)} to    about ⅘ of the depth of the container,-   (10) the production method according to term (1) or (2) above    wherein the thickness of the frozen layer of the sustained-release    preparation suspension is {fraction (1/1,000)} to about ⅘ of the    depth of the container,-   (11) the production method according to term (1) or (2) above    wherein the size of the container is about 5 mm to about 7,000 mm in    width, about 5 mm to about 7,000 mm in length, and about 1 mm to 100    mm in depth, and wherein the ice layer is about 0.01 mm to about 30    mm,-   (12) the production method according to any one of terms (1)    through (11) above wherein said sustained-release preparation is a    sustained-release preparation containing a biologically active    peptide,-   (13) the production method according to any one of terms (1)    through (11) above wherein said sustained-release preparation is a    sustained-release preparation containing a biologically active    peptide and a biodegradable polymer,-   (14) the production method according to term (12) or (13) above    wherein said biologically active peptide is an LH-RH agonist or    LH-RH antagonist,-   (15) the production method according to term (12) or (13) above    wherein said biologically active peptide is    5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH—C₂H₅ (leuprorelin) or    a salt thereof,-   (16) the production method according to term. (12) or (13) above    wherein said biologically active peptide is the acetate of    5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH—C₂H₅ (leuprorelin),-   (17) the production method according to term (13) above wherein said    biodegradable polymer is an α-hydroxycarboxylic acid polymer,-   (18) the production method according to term (17) above wherein said    α-hydroxycarboxylic acid polymer is a lactic acid-glycolic acid    polymer,-   (19) the production method according to term (18) above wherein the    content ratio of lactic acid and glycolic acid is about 100/0 to    about 40/60 (mol %),-   (20) the production method according to term (18) above wherein the    weight-average molecular weight of the polymer is about 3,000 to    about 100,000,-   (21) the production method according to term (13) above wherein said    biodegradable polymer is polylactic acid, and-   (22) the production method according to term (21) above wherein the    weight-average molecular weight of the polylactic acid is about    10,000 to about 60,000.

Sustained-release preparations for the production method of the presentinvention include, for example, microspheres. The term microsphere, asused herein, is understood to include microcapsules and microparticles.Specifically, there may be used the microspheres, microcapsules, or thelike, described in Japanese Patent Unexamined Publication Nos.100516/1985, 201816/1987, 124814/1990, 321622/1992, 112468/1993,194200/1993, 293636/1994, 145046/1994, 192068/1994, 169818/1996,132524/1997, 221417/1997 and 221418/1997, and elsewhere.

The drug contained in the above-described sustained-release preparationis preferably a biologically active peptide, exemplified by biologicallyactive peptides having molecular weights of about 300 to about 40,000,preferably about 400 to about 30,000, and more preferably about 500 toabout 20,000.

Preferably, such biologically active peptide have a basic group capableof forming a salt with a weak acid having a pKa value of not less than4.0 (e.g., carbonic acid, bicarbonic acid, boric acid, loweralkane-monocarboxylic acids having 1 to 3 carbon atoms). Saidbiologically active peptide may have an acidic group, whether free orsalt form, in addition to a basic group.

A representative activity of said biologically active peptides ishormone action. Said biologically active peptide may be a naturallyoccurring substance, synthetic substance, semi-synthetic substance, orgenetic engineering product, and may also be an analog and/or derivativethereof. The mechanism of action of these biologically active peptidesmay be agonistic or antagonistic.

Said biologically active peptide is exemplified by luteinizinghormone-releasing hormone (also referred to as LH-RH orgonadotropin-releasing hormone, Gn-RH), insulin, somatostatin,somatostatin derivatives (e.g., Sandostatin; U.S. Pat. Nos. 4,087,390,4,093,574, 4,100,117 and 4,253,998), growth hormone (GH), growthhormone-releasing hormone (GH-RH), prolactin, erythropoietin (EPO),adrenocorticotropic hormone (ACTH), ACTH derivatives (e.g., ebiratide),melanocyte-stimulating hormone (MSH), thyroid hormone-releasing hormone((pyr)Glu-His-ProNH₂; TRH), salts and derivatives thereof (JapanesePatent Unexamined Publication Nos. 121273/1975 and 116465/1977),thyroid-stimulating hormone (TSH), luteinizing hormone (LH),follicle-stimulating hormone (FSH), vasopressin, vasopressin derivatives(e.g., desmopressin), oxytocin, calcitonin, glucagon, gastrin, secretin,pancreozymin, cholecystokinin, angiotensin, human placental lactogen,human chorionic gonadotropin (HCG), enkephalin, enkephalin derivatives(e.g., U.S. Pat. No. 4,277,394, EP-31567), endorphin, kyotorphin,interferons (e.g., interferon-α, β-, -γ), interleukins (e.g.,interleukins 1 through 12), tuftsin, thymopoietin, thymosin,thymostimulin, thymic humoral factor (THF), blood thymic factor (FTS)and derivatives thereof (U.S. Pat. No. 4,229,438), tumor necrosis factor(TNF), colony-stimulating factors (e.g., CSF, GCSF, GMCSF, MCSF),motilin, dynorphin, bombesin, neurotensin, caerulein, bradykinin, atrialnatriuresis-increasing factor, nerve growth factor (NGF), cell growthfactors (e.g., EGF, TGF-β, PDGF, acidic FGF, basic FGF), neurotrophicfactors (e.g., NT-3, NT-4, CNTF, GDNF, BDNF), endothelin-antagonisticpeptides and analogs (derivatives) thereof (EP-436189, EP-457195,EP-496452, Japanese Patent Unexamined Publication Nos. 94692/1991 and130299/1991), insulin receptors, insulin-like growth factor (IGF)-1receptor, IGF-2 receptor, transferrin receptor, epidermal growth factor,low-density lipoprotein (LDL) receptor, macrophage scavenger receptor,GLUT-4-transporter, growth hormone receptor, leptin receptorinternalization-inhibiting MHC-I (major histocompatibility class Iantigen complex) al domain-derived peptide (Proceedings of the NationalAcademy of Sciences of the United States of America, Vol. 91, pp.9086-9090 (1994); ibid., Vol. 94, pp. 11692-11697 (1997)) and analogs(derivatives) thereof, and fragments thereof and fragment derivativesthereof.

When the biologically active peptide is a salt, the salt is exemplifiedby pharmacologically acceptable salts. For example, when saidbiologically active peptide has a basic group such as an amino group inthe molecular structure thereof, such salts include salts of said basicgroup and inorganic acids (e.g., hydrochloric acid, sulfuric acid,nitric acid, boric acid), organic acids (e.g., carbonic acid, bicarbonicacid, succinic acid, acetic acid, propionic acid, trifluoroacetic acid)etc. When said biologically active peptide has an acidic group such as acarboxyl group in the molecular structure thereof, such salts includesalts with inorganic base materials (e.g., alkali metals such as sodiumand potassium, alkaline earth metals such as calcium and magnesium),organic base materials (e.g., organic amines such as triethylamine,basic amino acids such as arginine) etc. The biologically active peptidemay form a metal complex compound (e.g., copper complex, zinc complex).

Preferred examples of the biologically active peptide for the presentinvention include LH-RH analogs or salts thereof that are effectiveagainst diseases dependent on LH-RH or hormones derived therefrom, suchas prostatic cancer, prostatic hypertrophy, endometriosis, hysteromyoma,metrofibroma, precocious puberty and breast cancer, and effective forcontraception, and somatostatin derivatives and salts thereof that areeffective against diseases dependent on growth hormone or hormonesderived therefrom, and gastrointestinal diseases such as digestiveulcer.

Examples of such LH-RH analogs include, for example, the peptidesdescribed in “Treatment with GnRH Analogs: Controversies andPerspectives” (The Parthenon Publishing Group Ltd., published 1996),Japanese Patent Examined Publication No. 503165/1991, Japanese PatentUnexamined Publication Nos. 101695/1991, 97334/1995 and 259460/1996, andelsewhere.

Biologically active peptides possessing LH-RH antagonistic action (LH-RHantagonists) include, for example, biologically active peptidesrepresented by general formula [Ia]:X-D2Nal-D4ClPhe-D3Pal-Ser-A-B-Leu-C-Pro-DAlaNH₂

-   -   [X represents N(4H₂-furoyl)Gly or NAc; A represents a residue        selected from NMeTyr, Tyr, Aph(Atz) and NMeAph(Atz); B        represents a residue selected from DLys(Nic), DCit,        DLys(AzaglyNic), DLys(AzaglyFur), DhArg(Et₂), DAph(Atz) and        DhCi; C represents Lys(Nisp), Arg or hArg(Et₂)] or salts        thereof. These peptides can be produced by the methods described        in the above-mentioned references or patent publications, or        methods based thereon.

Biologically active peptides possessing LH-RH agonistic action (LH-RHagonists) include, for example, biologically active peptides representedby general formula [Ib]:5-oxo-Pro-His-Trp-Ser-Tyr-Y-Leu-Arg-Pro-Z

-   -   [Y represents a residue selected from DLeu, DAla, DTrp,        DSer(tBu), D2NaI and DHis(ImBzl); Z represents NH—C₂H₅ or        Gly-NH₂] or salts thereof. Peptides wherein Y is DLeu and Z is        NH—C₂H₅, in particular, are preferred. These peptides can be        produced by the methods described in the above-mentioned        references or patent publications, or methods based thereon.

Examples of somatostatin derivatives or salts thereof are described in,for example, the Proceedings of the National Academy of Sciences of theUnited States of America, Vol. 93, pp. 12513-12518 (1996), and thereferences cited therein.

Of the somatostatin derivatives, those that are selectively effectiveagainst tumors include, for example, the biologically active peptidesdescribed in the patent publications for U.S. Pat. No. 5,480,870 andEP-05056800, and salts thereof, such as

Sandostatin (U.S. Pat. Nos. 4,087,390, 4,093,574, 4,100,117, 4,253,998)etc. are also preferred.

Of the above-mentioned biologically active peptides,5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro—NH—C₂H₅ (leuprorelin) or asalt thereof (especially acetate) is preferred.

The abbreviations used herein are defined as follows: Abbreviation NameN(4H₂-furoyl)Gly N-tetrahydrofuroylglycine residue NAc N-acetyl groupD2Nal D-3-(2-naphthyl)alanine residue D4ClPheD-3-(4-chlorophenyl)alanine residue D3Pal D-3-(3-pyridyl)alanine residueNMeTyr N-methyltyrosine residue Aph(Atz) N-[5′-(3′-amino-1′H-1′, 2′, 4′-triazolyl)]phenylalanine residue NMeAph(Atz) N-methyl-[5′-(3′-amino-1′H-1′, 2′, 4′-triazolyl)]phenylalanine residue DLys(Nic)D-(ε-N-nicotinoyl)lysine residue Dcit D-citrulline residueDLys(AzaglyNic) D-(azaglycylnicotinoyl)lysine residue DLys(AzaglyFur)D-(azaglycylfuranyl)lysine residue DhArg(Et₂)D-(N,N′-diethyl)homoarginine residue DAph(Atz) D-N-[5′-(3′-amino-1′H-1′,2′, 4′- triazolyl)]phenylalanine residue DhCi D-homocitrulline residueLys(Nisp) (ε-N-isopropyl)lysine residue hArg(Et₂)(N,N′-diethyl)homoarginine residue DSer(tBu) D-(O-t-butyl)serine residueDHis(ImBzl) D-(π-benzyl)histidine residueThe abbreviations for amino acids are based on abbreviations specifiedby the IUPAC-IUB Commission on Biochemical Nomenclature [EuropeanJournal of Biochemistry, Vol. 138, pp. 9-37 (1984)] or abbreviations incommon use in relevant fields. When an optical isomer may be present inamino acid, it is of the L-configuration, unless otherwise stated.

Sustained-release base materials used in the above-describedsustained-release preparation are preferably biodegradable polymersetc., exemplified by polymers and copolymers that have been synthesizedfrom one or more kinds selected from α-hydroxycarboxylic acids (e.g.,glycolic acid, lactic acid, hydroxybutyric acid), hydroxydicarboxylicacids (e.g., malic acid), hydroxytricarboxylic acids (e.g., citric acid)etc., and that have a free carboxyl group, or mixtures thereof;poly-α-cyanoacrylic acid esters; polyamino acids (e.g.,poly-γ-benzyl-L-glutamic acid); and maleic anhydride copolymers (e.g.,styrene-maleic acid copolymers).

Polymerization may be of the random, block or graft type. When theabove-mentioned α-hydroxycarboxylic acids, hydroxydicarboxylic acids andhydroxytricarboxylic acids have an optical active center in theirmolecular structures, they may be of the D-, L- or DL-configuration. Ofthese, lactic acid-glycolic acid polymers, poly-α-cyanoacrylic acidesters etc. are preferred. Greater preference is given to lacticacid-glycolic acid polymers.

The biodegradable polymer is preferably biodegradable polymer or lacticacid-glycolic acid copolymer consisting of a mixture of (A) a copolymerof glycolic acid and a hydroxycarboxylic acid represented by the generalformula:

wherein R represents an alkyl group having 2 to 8 carbon atoms, and (B)a polylactic acid.

With respect to general formula [II] above, the linear or branched alkylgroup represented by R, which has 2 to 8 carbon atoms, is exemplified byethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,pentyl, isopentyl, neopentyl, tert-pentyl, 1-ethylpropyl, hexyl,isohexyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl and2-ethylbutyl. Preferably, a linear or branched alkyl group having 2 to 5carbon atoms is used. Such alkyl groups include, for example, ethyl,propyl, isopropyl, butyl and isobutyl. More preferably, R is ethyl.

The hydroxycarboxylic acid represented by general formula [II] isexemplified by 2-hydroxybutyric acid, 2-hydroxyvaleric acid,2-hydroxy-3-methylbutyric acid, 2-hydroxycaproic acid,2-hydroxyisocaproic acid and 2-hydroxycapric acid, with preference givento 2-hydroxybutyric acid, 2-hydroxyvaleric acid,2-hydroxy-3-methylbutyric acid and 2-hydroxycaproic acid, with greaterpreference given to 2-hydroxybutyric acid. Although thehydroxycarboxylic acid may be of the D-, L- or D,L-configuration, it ispreferable to use a mixture of the D- and L-configurations wherein theratio of the D-/L-configuration (mol %) preferably falls within therange from about 75/25 to about 25/75, more preferably from about 60/40to about 40/60, and still more preferably from about 55/45 to about45/55.

With respect to the copolymer of glycolic acid and a hydroxycarboxylicacid represented by general formula [II] (hereinafter referred to asglycolic acid copolymer), copolymerization may be of the random, blockor graft type. A random copolymer is preferred.

The hydroxycarboxylic acid represented by general formula [II] may beused singly or in a mixture of one or more kinds in a given ratio.

With respect to the content ratio of glycolic acid and thehydroxycarboxylic acid represented by general formula [II] in glycolicacid copolymer (A) above, it is preferable that glycolic acid accountfor about 10 to about 75 molt and hydroxycarboxylic acid for theremaining portion. More preferably, glycolic acid accounts for about 20to about 75 mol %, and still more preferably about 40 to about 70 mol %,and hydroxycarboxylic acid for the remaining portion. The weight-averagemolecular weight of the glycolic acid copolymer is normally about 2,000to about 100,000, preferably about 3,000 to about 80,000, and morepreferably about 5,000 to about 50,000. The degree of dispersion of theglycolic acid copolymer (weight-average molecular weight/number-averagemolecular weight) is preferably about 1.2 to about 4.0, more preferablyabout 1.5 to about 3.5.

Glycolic acid copolymer (A) above can be produced by a known productionmethod such as that described in Japanese Patent Unexamined PublicationNo. 28521/1986.

Although the polylactic acid may be of the D- or L-configuration or amixture thereof, it is preferable that the ratio of theD-/L-configuration (mol %) fall within the range from about 75/25 toabout 20/80. The ratio of the D-/L-configuration (mol %) is morepreferably about 60/40 to about 25/75, and still more preferably about55/45 to about 25/75. The weight-average molecular weight of saidpolylactic acid is preferably about 1,500 to about 100,000, morepreferably about 2,000 to about 80,000, and still more preferably about3,000 to about 50,000 or about 10,000 to 60,000 (more preferably about15,000 to about 50,000). Also, the degree of dispersion of thepolylactic acid is preferably about 1.2 to about 4.0, more preferablyabout 1.5 to about 3.5.

For producing a polylactic acid, two methods are known: ring-openingpolymerization of lactide, a dimer of lactic acid, and dehydrationpolymerization condensation of lactic acid.

Glycolic acid copolymer (A) and polylactic acid (B) in the preparationbase material of the present invention are used in a mixture wherein the(A)/(B) ratio (% by weight) falls within the range from about 10/90 toabout 90/10. The mixing ratio (% by weight) is preferably about 20/80 toabout 80/20, and more preferably about 30/70 to about 70/30.

If either component (A) or (B) is in excess, the preparation obtainedshows a drug release pattern no more than that obtained with the use ofcomponent (A) or (B) alone; no linear release pattern is expected in thelast stage of drug release from the mixed base material. Although thedecomposition/elimination rate of glycolic acid copolymer and polylacticacid varies widely, depending on molecular weight or composition, drugrelease duration can be extended by increasing the molecular weight ofpolylactic acid added or lowering the mixing ratio (A)/(B), since thedecomposition/elimination rate of glycolic acid copolymer is usuallyhigher than that of polylactic acid. Conversely, drug release durationcan be shortened by decreasing the molecular weight of polylactic acidadded or increasing the mixing ratio (A)/(B). Drug release duration canalso be adjusted by altering the kind and content ratio ofhydroxycarboxylic acid represented by general formula [II].

When the biodegradable polymer used is polylactic acid or a lacticacid-glycolic acid copolymer (hereinafter simply referred to as lacticacid-glycolic acid polymer), the lactic acid/glycolic acid content ratio(mol %) is preferably 100/0 to 40/60, more preferably 100/0 to 45/55,and still more preferably 100/0 to 50/50.

The weight-average molecular weight of the lactic acid-glycolic acidpolymer is preferably 3,000 to 100,000, more preferably 5,000 to 80,000.The degree of dispersion (weight-average molecular weight/number-averagemolecular weight) is preferably about 1.3 to about 4.0, more preferablyabout 1.5 to about 3.5.

The decomposition/elimination rate of lactic acid-glycolic acid polymervaries widely, depending on composition or molecular weight. However,drug release duration can be extended by lowering the glycolic acidratio or increasing the molecular weight, becausedecomposition/elimination is usually delayed as the glycolic acid ratiodecreases. Conversely, drug release duration can be shortened byincreasing the glycolic acid ratio or decreasing the molecular weight.To obtain a sustained-release preparation(solid) of the long acting type(e.g., 1-6 months, preferably 1-4 months), it is preferable to use alactic acid-glycolic acid polymer whose content ratio and weight-averagemolecular weight fall in the above ranges. If choosing a lacticacid-glycolic acid polymer that decomposes more rapidly than that whosecontent ratio and weight-average molecular weight fall in the aboveranges, initial burst is difficult to suppress; if choosing a lacticacid-glycolic acid polymer that decomposes more slowly than that whosecontent ratio and weight-average molecular weight fall in the aboveranges, it is likely that no effective amount of drug is released duringsome period.

Weight-average molecular weight, number-average molecular weight anddegree of dispersion, as defined herein, are polystyrene-based molecularweights and degree of dispersion determined by gel permeationchromatography (GPC) with nine polystyrenes as reference substances withweight-average molecular weights of 120,000, 52,000, 22,000, 9,200,5,050, 2,950, 1,050, 580, and 162, respectively. Measurements are takenusing a GPC column KF804Lx2 (produced by Showa Denko) and an R1 monitorL-3300 (produced by Hitachi, Ltd.), with chloroform as a mobile phase.Also, number-average molecular weight is calculated by dissolving thebiodegradable polymer in an acetone-methanol mixed solvent, andtitrating this solution with an alcoholic solution of potassiumhydroxide with phenolphthalein as an indicator, to determine theterminal carboxyl group content. This molecular weight is hereinafterreferred to as number-average molecular weight based on terminal groupquantitation.

While the number-average molecular weight based on terminal groupquantitation is an absolute value, that based on GPC measurement is arelative value that varies depending on various analytical conditions(e.g., kind of mobile phase, kind of column, reference substance, slicewidth, baseline); it is therefore difficult to have an absolutenumerical representation of both values. In the case of polymers havinga free carboxyl group at one end, that have been synthesized from lacticacid and glycolic acid by the catalyst-free dehydration polymerizationcondensation method, however, the number-average molecular weights basedon GPC measurement and terminal group quantitation almost agree witheach other. This fact means that the number-average molecular weightbased on terminal group quantitation falls within the range from about0.5 to about 2 times, preferably from about 0.7 to about 1.5 times, thatbased on GPC measurement.

A lactic acid-glycolic acid polymer can be produced by, for examplecatalyst-free dehydration polymerization condensation from a lactic acidand a glycolic acid, or ring-opening polymerization from a lactide and acyclic compound such as glycolide by means of a catalyst (EncyclopedicHandbook of Biomaterials and Bioengineering Part A: Materials, Volume 2,Marcel Dekker, Inc., 1995).

Although the polymer synthesized by ring-opening polymerization is apolymer not having a carboxyl group, it is also possible to use apolymer prepared by chemically treating said polymer to render itsterminal a free carboxyl group [Journal of Controlled Release, Vol. 41,pp. 249-257 (1996)].

The above-described lactic acid-glycolic acid polymer having a freecarboxyl group at one end can be produced without any problems by knownproduction methods (e.g., catalyst-free dehydration polymerizationcondensation method, see Japanese Patent Unexamined Publication No.28521/1986); a polymer having a free carboxyl group elsewhere (notlimited to terminals) can be produced by known production methods (e.g.,see Patent Publication for WO94/15587).

Also, the lactic acid-glycolic acid polymer prepared by chemicaltreatment after ring-opening polymerization to render its terminal afree carboxyl group may be a commercial product of Boehringer IngelheimKG, for example.

The sustained-release preparation suspension used for the productionmethod of the present invention is a suspension prepared by addinganticoagulants mentioned below. In case of MC, the sustained-releasepreparation suspension is usually prepared about 1 mg to about 300mg/ml, preferably, about 5 mg to about 1000 mg/ml for MC.

The sustained-release preparation suspension used for the productionmethod of the present invention is a suspension prepared by adding ananticoagulant, e.g., a water-soluble saccharide [e.g., mannitol,lactose, glucose, starches (e.g., corn starch)], amino sugars (e/g/.glycine, alanine), protein (e.g., gelatin, fibrin, collagen), inorganicsalt (e.g., sodium chloride, sodium bromide, potassium carbonate), orthe like. Of these anticoagulants, mannitols, such as D-mannitol, arepreferred.

Solvents for the suspension include, for example, water for injection(e.g., water produced by distillation, ultrafiltration etc.), UF water,RO water, ion exchange water, volatile solvents (e.g., ethanol,acetone), polyethylene glycol, vegetable oils, mineral oils, or mixturesthereof, with preference given to water for injection etc.

Also, surfactants, thickening agents, pH regulators etc. can be added assuspension stabilizers. Useful surfactants include, for example,polysorbates (e.g., polysorbate 80, polysorbate 20), Pluronics (e.g.,Pluronic F68 (nonproprietary name polyoxyethylene [160] polyoxypropylene[30] glycol etc.), and polyoxyethylene hardened castor oils (e.g.,polyoxyethylene hardened castor oil 50, polyoxyethylene hardened castoroil 60). Useful thickening agents include, for example, carboxymethylcelluloses (e.g., CMC-K, CMC-Na) and polyvinylpyrrolidone (PVP). UsefulpH regulators include, for example, hydrochloric acid, sodium hydroxide,acetic acid, lactic acid, ammonium hydroxide, sodium carbonate, andsodium hydrogen carbonate.

The freeze-drying container for the production method of the presentinvention may be any container, as long as it is in common use forfreeze-drying of sustained-release preparations such as MCs; forexample, freeze-drying trays etc. are used. Said container is made of ametal (preferably stainless steel (SUS316, 304 etc.), glass, orporcelain. Further, the freeze-drying container for the productionmethod of the present invention may be a plate form.

The size of said freeze-drying container may be chosen as appropriateaccording to freeze-drying scale. Specifically, freeze-drying containers{circle over (1)} about 5 mm to about 10,000 mm in width, about 5 mm toabout 10,000 mm in length, and about 0.1 mm to about 500 mm in depth,preferably {circle over (2)} about 5 mm to about 7,000 mm in width,about 5 mm to about 7,000 mm in length, and about 1 mm to about 100 mmin depth, and more preferably {circle over (3)} about 5 mm to about 500mm in width, about 5 mm to about 300 mm in length, and about 5 mm toabout 100 mm in depth, for example, are used. Although thewidth/length/depth ratio is not subject to limitation, it is normallyabout 1 to about 20 in width and about 1 to about 10 in length,preferably about 1 to about 10 in width and about 1 to about 6 inlength, per 1 in depth.

The container capacity is, for example, about 10 ml to about 100,000 ml,preferably about 100 ml to about 5,000 ml, and more preferably about3,000 ml.

Said freeze-drying container is partially hollowed for aspiration duringfreeze-drying, and normally has no ceiling plate.

The water-repelling base material used to cover said freeze-dryingcontainer is exemplified by ethylene fluoride resins (e.g., ethylenetetrafluoride resin, ethylene trifluoride resin, ethylene difluorideresin), vinylidene fluoride resin, propylene hexafluoride-ethylenetetrafluoride copolymer resin, modified fluorine resin, ethylenetetrafluoride resin-perfluoroalkoxyethylene copolymer resin, andethylene tetrafluoride resin-ethylene copolymer resin, with preferencegiven to ethylene fluoride resins (e.g., ethylene tetrafluoride resin,ethylene trifluoride resin, ethylene difluoride resin), specificallyTeflon (trade name).

The freeze-drying container can be coated with a water-repelling basematerial by commonly known methods or methods based thereon,specifically plating, vapor deposition etc.

The solid sustained-release preparation obtained by the productionmethod of this invention, includes any sustained-release preparationsobtainable by the production method of this invention (i.e.freeze-drying method). The solid sustained-release preparation obtainedby the production method of this invention includes a sustained-releasepreparation powder (e.g. MC powder), and also includes sustained-releasepreparations manufactured in various forms by known methods (e.g. pelletform, needle form, etc.).

The production method of the present invention is hereinafter describedin more details.

(1) Production method for a solid sustained-release preparation,characterized in that a sustained-release preparation (asustained-release preparation suspension) is freeze-dried in afreeze-drying container whose inner face is partially or totally coatedwith an ice layer.

The water used to prepare an ice layer is exemplified by water forinjection (e.g., distilled water) and ion exchange water.

The portion covered with an ice layer is a portion of, or the entire,inner face of the freeze-drying container; for example, it may be thebottom face alone, the entire bottom and side faces, a portion of thebottom face alone, or a portion of the bottom and side faces alone. Theouter face of the container may also be coated with a water-repellingbase material.

The thickness of the ice layer in the freeze-drying container may bechosen as appropriate according to the size of the container used,sustained-release preparation (sustained-release preparation suspension)volume, freeze-drying temperature, and other factors; for example, thethickness is normally about {fraction (1/1,000)} to about ⅘, preferablyabout {fraction (1/500)} to about ⅕, more preferably about {fraction(1/100)} to about {fraction (1/10)}, and still more preferably about{fraction (1/10)}, of the depth of the container, with preference givento thicknesses of not less than about 0.01 mm. More specifically, thethickness is normally about 0.01 mm to about 400 mm, preferably about0.01 mm to about 200 mm, more preferably about 0.01 mm to about 30 mm,still more preferably about 0.1 mm to about 30 mm, yet still morepreferably about 0.1 mm to about 10 mm, and most preferably about 1 mm.

An ice layer is prepared by dispensing water into the tray, and normallyfreezing it at about −80° C. to about 0° C., preferably about −50° C. toabout 0° C.

After the ice layer is formed in the freeze-drying container, asustained-release preparation (a sustained-release preparationsuspension) is dispensed into the container and frozen to form a frozenlayer of the sustained-release preparation (sustained-releasepreparation suspension).

In the case of microcapsules, the sustained-release preparation(sustained-release preparation suspension) is normally prepared to about1 mg to about 300 mg/ml, preferably about 5 mg to about 1,000 mg/ml formicrocapsule.

The volume of the sustained-release preparation (sustained-releasepreparation suspension) in the freeze-drying container may be chosen asappropriate according to the size of the container used, freeze-dryingtemperature, and other factors; for example, the thickness of the frozenlayer of the sustained-release preparation (sustained-releasepreparation suspension) is normally about {fraction (1/1,000)} to about⅘, preferably about {fraction (1/500)} to about ⅕, more preferably about{fraction (1/100)} to about {fraction (1/10)}, and still more preferablyabout {fraction (1/10)}, of the depth of the container. The volume ofthe sustained-release preparation (sustained-release preparationsuspension) may also be about 0.1 ml to about 99.9 ml, preferably about1 ml to about 90 ml, and more preferably about 1 ml to about 40 ml, per100 ml container capacity. When the ice layer is about 1 mm from thebottom of the container, the frozen layer of the sustained-releasepreparation (sustained-release preparation suspension) may be about 1 to10 times, preferably about 1 to 5 times, as thick as the ice layer.

For example, when the container used is about 5 mm to about 7,000 mm inwidth, about 5 mm to about 7,000 mm in length, and about 1 mm to 100 mmin depth, the ice layer thickness is normally about 0.01 mm to about 30mm, preferably about 0.1 mm to about 30 mm, more preferably about 0.1 mmto 10 mm, and still more preferably about 1 mm. On the other hand, thefrozen layer of the sustained-release preparation (sustained-releasepreparation suspension) is, for example, about 1 mm to about 20 mm,preferably about 2 mm to about 10 mm, and more preferably about 4 mm,from the bottom face ice layer.

The frozen layer of the sustained-release preparation (sustained-releasepreparation suspension) is prepared by dispensing a sustained-releasepreparation (a sustained-release preparation suspension), whichpreviously cooled to about −10° C. to about 20° C., preferably about 0°C. to 5° C., onto the ice layer, then normally freezing it about −80° C.to about 0° C., preferably about −50° C. to about 0° C.

Two layers, i.e., an ice layer and a frozen layer of thesustained-release preparation (sustained-release preparationsuspension), are thus prepared in the freeze-drying container.

Freeze-drying can be achieved by commonly known methods; for example, itcan be achieved as directed in the above-mentioned patent publicationsthat disclose microcapsules or microspheres.

Preferably, the freeze-drying can be achieved, for example, bycompleting the sublimation of frozen water in the freeze-dryingcontainer under reduced condition that the temperature in thefreeze-drying container is 0 or below (preferably, −40° C. to 0° C.,more preferably, −20% to 0° C., further preferably, −10° C. to 0° C.More concretely, the freeze-drying can be achieved, by completing thesublimation of frozen water in the freeze-drying container under reducedcondition that the temperature in the freeze-drying container (shelftemperature) is maintained 0° C. or below (preferably, −40° C. to 0° C.,more preferably, −20° C. to 0° C., further preferably, −10% to 0° C.).

The temperature of the freeze-drying container (shelf temperature),mentioned above means the temperature of the container holding thefreeze-drying samples or the temperature of the shelf contacting withthe container. The frozen water, mentioned above means frozenfree-water.

When the freeze-drying container (shelf temperature) is maintained 0 orbelow (preferably, −40° C. to 0° C., more preferably, −20° C. to 0° C.,further preferably, −10° C. to 0° C.), the temperature is maintained formore than about 0.1 hours, preferably for about 1 hour to about 500hours, more preferably for about 5 hours to about 100 hours in order tocompleting the sublimation of frozen water in the freeze-dryingcontainer.

Under the freeze-drying method, mentioned above, the frozen water issublimated the temperature of 0 or below, that is, the temperature belowthe eutectic crystal or melting point, and the temperature in which theice does not melt and the freeze-drying method provides the preventionof the collapsing of the freeze-drying cake, the prevention of thescattering of the MC powders around the outside of the freeze-dryingcontainer, high yield of the MC powders and obtaining the high quarityof the MC powders.

(2) Production method for a solid sustained-release preparation,characterized in that a sustained-release preparation (asustained-release preparation suspension) is freeze-dried in afreeze-drying container whose inner face is partially or totally coatedwith a water-repelling base material.

The portion covered with a water-repelling base material is a portionof, or the entire, inner face of the freeze-drying container; forexample, it may be the bottom face alone, the entire bottom and sidefaces, a portion of the bottom face alone, or a portion of the bottomand side faces alone. The outer face of the container may also be coatedwith a water-repelling base material.

A sustained-release preparation (a sustained-release preparationsuspension) is dispensed to a container and frozen to form a frozenlayer of the sustained-release preparation (sustained-releasepreparation suspension).

In the case of microcapsules, the sustained-release preparation(sustained-release preparation suspension) is normally prepared to about1 mg to about 300 mg/ml, preferably about 1 mg to about 300 mg/ml formicrocapsule.

The volume of the sustained-release preparation (sustained-releasepreparation suspension) in the freeze-drying container may be chosen asappropriate according to the size of the container used, freeze-dryingtemperature, and other factors; for example, the thickness of the frozenlayer of the sustained-release preparation (sustained-releasepreparation suspension) is normally about {fraction (1/1,000)} to about⅘, preferably about {fraction (1/500)} to about ⅕, more preferably about{fraction (1/100)} to about {fraction (1/10)}, and still more preferablyabout {fraction (1/10)}, of the depth of the container. The volume ofthe sustained-release preparation (sustained-release preparationsuspension) may also be about 0.1 ml to about 99.9 ml, preferably about1 ml to about 90 ml, and more preferably about 1 ml to about 40 ml, per100 ml container capacity. When the ice layer is about 1 mm from thebottom of the container, the frozen layer of the sustained-releasepreparation (sustained-release preparation suspension) may be about 1 to10 times, preferably about 1 to 5 times, as thick as the ice layer.

For example, when the container used is about 5 mm to about 7,000 mm inwidth, about 5 mm to about 7,000 mm in length, and about 1 mm to 100 mmin depth, the ice layer thickness is normally about 0.01 mm to about 30mm, preferably about 0.1 mm to about 30 mm, more preferably about 0.1 mmto 10 mm, and still more preferably about 1 mm. On the other hand, thefrozen layer of the sustained-release preparation (sustained-releasepreparation suspension) is, for example, about 1 mm to about 20 mm,preferably about 2 mm to about 10 mm, and more preferably about 4 mm,from the bottom face ice layer.

The frozen layer of the sustained-release preparation (sustained-releasepreparation suspension) is prepared by dispensing a sustained-releasepreparation (a sustained-release preparation suspension), which ispreviously cooled to about −10° C. to about 20° C., preferably about 0°C. to 5° C., onto the ice layer, then normally freezing it about −80° C.to about 0° C., preferably about −50° C. to about 0° C.

A frozen layer of the sustained-release preparation (sustained-releasepreparation suspension) is thus prepared in the freeze-drying container.

Freeze-drying can be achieved in the same manner as in production method(1) above.

(3) Production method for a solid sustained-release preparation,characterized in that a sustained-release preparation (asustained-release preparation suspension) is freeze-dried in afreeze-drying container whose inner face is coated with awater-repelling base material and partially or totally coated with anice layer.

This method can be conducted in the same manner as production method (1)except that the freeze-drying container for production method (1) isreplaced with a freeze-drying container whose inner face is coated witha water-repelling base material.

In this method, it is desirable that at least the entire portion of theinner face of the freeze-drying container, that comes in contact withthe sustained-release preparation (sustained-release preparationsuspension), be coated with a water-repelling base material.

The production method of the present invention has the advantageousshown below.

(1) Because MC powders do not adhere to the tray, there is no need forMC powders removal using a scraper at time of their recovery.

(2) Because of obviation of the necessity of MC powders removal using ascraper, environmental exposure time at time of MC powders recovery isshortened, thus reducing the risk of invation of microorganisms etc.Also, because of the short environmental exposure time, the risk isreduced from the viewpoint of physicochemical stability, since MCs needwater content control.

(3) Because of obviation of the necessity of MC powders removal using ascraper, there is no risk of production and entry of foreign substancesdue to friction between the tray and scraper.

(4) Because of minimum adhesion of MC powders and the tray, the MCpowders recovery rate is high.

(5) Moreover, by using the freeze-drying method, mentioned above, MCpowders are more constantly recoverd and recoverd in more high yield.

Where necessary, freeze-drying of a sustained-release preparation (asustained-release preparation suspension) by the production method ofthe present invention may be followed by heating under reduced pressurewithout causing mutual adhesion of sustained-release preparationparticles, to remove the water and organic solvent from thesustained-release preparation. In this case, it is preferable that thesuspension be heated at a temperature slightly higher than theintermediate glass transition point of the biodegradable polymer, asdetermined using a differential scanning calorimeter when thetemperature is increased at a rate of about 10 to about 20° C. perminute. More preferably, the suspension is heated within the temperaturerange from the intermediate glass transition point of the biodegradablepolymer to a temperature higher by about 30° C. than the glasstransition point. When a lactic acid-glycolic acid polymer is used asthe biodegradable polymer, in particular, it is preferable that thesuspension be heated within the temperature range from the intermediateglass transition point to a temperature higher by 20° C. than the glasstransition point, more preferably within the temperature range from theintermediate glass transition point to a temperature higher by 10° C.than the glass transition point.

Although it varies depending on the amount of sustained-releasepreparation and other factors, heating time is preferably about 12 hoursto about 168 hours, more preferably about 48 hours to about 120 hours,and still more preferably about 48 hours to about 96 hours, after thesustained-release preparation reaches a given temperature.

Any heating method can be used, as long as sustained-release preparationaggregates are uniformly heated.

Useful thermal drying methods include, for example, the method in whichthermal drying is conducted in a constant-temperature chamber, fluidizedbed chamber, mobile chamber or kiln, and the method using microwaves forthermal drying. Of these methods, the method in which thermal drying isconducted in a constant-temperature chamber is preferred.

The freeze-dried sustained-release preparation(solid) specimen thusobtained can be administered orally or non-orally as such or in the formof various dosage forms prepared using it as a starting material.Specifically, it can be administered as intramuscular, subcutaneous,visceral and other injectable preparations or implant preparations,nasal, rectal, uterine and other transdermal preparations, oralpreparations [e.g., solid preparations such as capsules (e.g., hardcapsules, soft capsules), granules and powders; liquids such as syrups,emulsions and suspensions] etc.

For example, the sustained-release preparation(solid) of the presentinvention can be prepared as injectable preparations by suspending inwater with a dispersing agent (e.g., surfactants such as Tween 80 andHCO-60, polysaccharides such as sodium hyaluronate, carboxymethylcellulose and sodium alginate), a preservative (e.g., methyl paraben,propyl paraben), an isotonizing agent (e.g., sodium chloride, mannitol,sorbitol, glucose, proline) etc. to yield an aqueous suspension, or bydispersing in a vegetable oil such as sesame oil or corn oil to yield anoily suspension, whereby a practically useful sustained-releaseinjectable preparation(solid) is obtained.

When the sustained-release preparation(solid) of the present inventionis used in the form of an injectable suspension, its particle diameteris chosen over such a range that the requirements concerning the degreeof dispersion and needle passage are met. For example, the mean particlediameter normally ranges from about 0.1 to 300 μm, preferably from about1 to 150 μm, and more preferably from about 2 to 100 pin.

The sustained-release preparation(solid) of the present invention can beprepared as a sterile preparation by such methods as the method in whichthe entire production process is aseptic, the method using gamma raysfor sterilization, and the method in which a preservative is added,which methods are not to be construed as limitative.

Because of low toxicity, the above-described sustained-releasepreparation(solid) can be used safely in humans or non-human mammals(e.g., monkeys, bovines, swines, dogs, cats, mice, rats, rabbits).

Although varying widely depending on kind, content and dosage form ofthe active ingredient biologically active peptide, and duration ofrelease of the biologically active peptide, target disease, subjectanimal species, method of administration and other factors, the dose ofthe sustained-release preparation(solid) may be set at any level, aslong as the biologically active peptide is effective. The dose of theactive ingredient biologically active peptide per administration can bepreferably chosen as appropriate over the range from about 0.001 mg to100 mg/kg body weight, more preferably from about 0.005 mg to 50 mg/kgbody weight, and still more preferably from about 0.01 mg to 10 mg/kgbody weight, per adult (50 kg body weight assumed) in the case of a1-month release preparation(solid).

More specifically, when an LH-RH antagonist represented by generalformula [Ia] or an LH-RH agonist represented by general formula [Ib], asdescribed above, is used as the biologically active peptide, thesustained-release preparation(solid) of the present invention can beused as therapeutic/prophylactic agents for hormone-dependent diseases,including prostatic cancer, prostatic hypertrophy, endometriosis,hysteromyoma, metrofibroma, precocious puberty, breast cancer,gallbladder cancer, uterine cervical cancer, chronic lymphatic leukemia,chronic myelocytic leukemia; colorectal cancer, gastritis, Hodgkin'sdisease, malignant melanoma, metastatic/multiple myeloma, non-Hodgkin'slymphoma, non-small cell lung cancer, ovarian cancer, digestive ulcer,systemic fungal infection, small cell lung cancer, cardiac valvulardisease, mastopathy, polycystic ovary, infertility, chronic anovulation,induction of appropriate ovulation in women, acnes, amenorrhea (e.g.,secondary amenorrhea), cystic diseases of ovary and breast (includingpolycystic ovary), gynecologic cancers, ovarian hyperandrogenemia andhypertrichosis, AIDS due to T cell production mediated via thymusblastogenesis, and male infertilization for treatment of male sexualcrime offenders, as drugs for contraception and mitigation of symptomsin premenstrual syndrome (PMS), as agents for in vitro fertilization(IVF), etc., and in particular, as therapeutic/prophylactic agents forprostatic cancer, prostatic hypertrophy, endometriosis, hysteromyoma,metrofibroma, precocious puberty etc., and as contraceptives.

Although varying widely depending on the dosage form of the biologicallyactive peptide, desired duration of drug release, target disease,subject animal species, and other factors, the dose of said biologicallyactive peptide may be set at any level, as long as the drug iseffective. The dose of the drug per administration can be preferablychosen as appropriate over the range from about 0.001 mg to about 10mg/kg body weight, more preferably from about 0.005 mg to about 5 mg/kgbody weight, per adult in the case of a 1-month sustained-releasepreparation(solid) for cancer.

The dose of the sustained-release preparation(solid) per administrationcan be preferably chosen as appropriate over the range from about 0.005mg to 50 mg/kg body weight, more preferably from about 0.01 mg to 30mg/kg body weight per adult. The frequency of administration can bechosen as appropriate, depending on kind, content and dosage form of theactive ingredient biologically active peptide, duration of release ofthe biologically active peptide, target disease, subject animal speciesand other factors, e.g., once every several weeks, one every month oronce every several months. Best Mode for Carrying Out the PresentInvention.

The present invention is hereinafter described in more detail by meansof the following working examples and reference examples, which are notto be construed as limitative, and which may be modified, as long as thescope of the present invention is not deviated from.

EXAMPLES Reference Example 1 Preparation of Sustained-Release MC(1-Month Preparation) Suspension

2.4 g of gelatin and 15.2 g of leuprorelin acetate were dissolved in15.0 g of distilled water under warming. To this solution, 321 g of aseparately prepared dichloromethane solution of a lactic acid-glycolicacid copolymer (hereinafter referred to as PLGA) [lactic acid/glycolicacid=75/25 (mol %), weight-average molecular weight 10,500] (121 g ofPLGA contained) was added, followed by emulsification with stirringusing a mini-mixer for 2 minutes (rotation rate 10,000 rpm). Thisemulsion was added to 25 l of a previously prepared 0.1% aqueoussolution of polyvinyl alcohol (PVA), followed by emulsification again.While this W/O/W emulsion was gently stirred, the solvent was removedover a period of about 3 hours. The MCs obtained were passed through a75 μm sieve to remove coarse particles, then centrifuged. The MCsseparated were washed with distilled water to remove the free drug andPVA, after which they were subjected to wet sieving through sieves of250 μm and 90 μm pore size in the presence of a small amount ofdistilled water. 18.4 g of D-mannitol was added to the productsuspension and dissolved to yield a MC suspension. The amounts ofindividual starting materials may be adjusted according to productionscale.

Reference Example 2 Preparation of Sustained-Release MC (3-MonthPreparation) Suspension

10.8 g of leuprorelin acetate was dissolved in 12.5 g of distilled waterunder warming. To this solution, 256 g of a separately prepareddichloromethane solution of a lactic acid polymer (hereinafter referredto as PLA) [weight-average molecular weight 16,000] (96 g of PLAcontained) was added, followed by emulsification during stirring using amini-mixer for 2 minutes (rotation rate 10,000 rpm). This emulsion wasadded to 25 l of a previously prepared 0.1% aqueous solution ofpolyvinyl alcohol (PVA), followed by emulsification again. While thisW/O/W emulsion was gently stirred, the solvent was removed over a periodof about 3 hours. The MCs obtained were passed through a 75 μm sieve toremove coarse particles, then centrifuged. The MCs separated were washedwith distilled water to remove the free drug and PVA, after which theywere subjected to wet sieving through sieves of 250 pn and 90 μm poresize in the presence of a small amount of distilled water. 18.4 g ofD-mannitol was added to the product suspension and dissolved to yield aMC suspension. The amounts of individual starting materials may beadjusted according to production scale.

Example 1

In a freeze-drying tray (width 200 mm, length 100 mm, depth 20 mm), anice layer about 1 mm in thickness was formed with water for injection at−30° C. An ice layer was also formed on the inner wall of the tray (icelining). 80 ml of the MC suspension as obtained in Reference Example 1above, previously cooled to about 5° C., was added onto thefreeze-drying tray with the ice layer, and thoroughly frozen at about−30° C., followed by freeze-drying by a conventional method.

Separately, 80 ml of said MC suspension was added onto a freeze-dryingtray without an ice layer, and thoroughly frozen at about −30° C.,followed by freeze-drying by a conventional method.

After freeze-drying, each tray was inverted, and the status ofdetaching/recovery of the freeze-dried specimen therefrom was observed.

When the freeze-drying tray with an ice layer was used, the freeze-driedspecimen was easily recovered from the tray, with no MC powder adhesionon the tray surface. On the other hand, when the freeze-drying traywithout an ice layer was used, the freeze-dried specimen was notdetached from the tray, with MC powder adhesion on the tray even afterpowder recovery using a scraper.

Example 2

80 ml of the MC suspension as obtained in Reference Example 1 above,previously cooled to about 5° C., was added to a freeze-drying tray(width 200 mm, length 100 mm, depth 20 mm), previously coated withTeflon (trade name), a water-repelling polymer, and thoroughly frozen atabout −30° C., followed by freeze-drying by a conventional method.

Separately, 80 ml of said MC suspension was added to a freeze-dryingtray without surface water-repelling treatment, and thoroughly frozen atabout −30° C., followed by freeze-drying by a conventional method.

After freeze-drying, each tray was inverted, and the status ofdetaching/recovery of the freeze-dried specimen therefrom was observed.

When the freeze-drying tray with surface water-repelling treatment wasused, the freeze-dried specimen was easily recovered from the tray, withno MC powder adhesion on the tray surface. On the other hand, when thefreeze-drying tray without surface water-repelling treatment was used,the freeze-dried specimen was not detached from the tray, with MC powderadhesion on the tray even after powder recovery using a scraper.

Example 3

In the same Teflon-coated freeze-drying tray (width 200 mm, length 100mm, depth 20 mm) as in Example 2, an ice layer about 1 mm in thicknesswas formed with water for injection at −30° C. An ice layer was alsoformed on the inner wall of the tray (ice lining). 80 ml of the MCsuspension as obtained in Reference Example 1 above, previously cooledto about 5° C., was added to the tray and thoroughly frozen at about−30° C., followed by freeze-drying by a conventional method.

Separately, 80 ml of said MC suspension was added onto a freeze-dryingtray without an ice layer and without surface water-repelling treatment,and thoroughly frozen at about −30° C., followed by freeze-drying by aconventional method.

After freeze-drying, each tray was inverted, and the status ofdetaching/recovery of the freeze-dried specimen therefrom was observed.

When the freeze-drying tray with surface water-repelling treatment andwith an ice layer was used, the freeze-dried specimen was easilyrecovered from the tray, with no MC powder adhesion on the tray surface.On the other hand, when the freeze-drying tray without an ice layer andwithout surface water-repelling treatment was used, the freeze-driedspecimen was not detached from the tray, with MC powder adhesion on thetray even after powder recovery using a scraper.

Example 4

Even when the freeze-drying tray size and ice layer thicknesses shown inTable 1 were combined variously, results similar to those in Examples 1through 3 were obtained. TABLE 1 Ice Layer Tray Bottom face Side faceLength (mm) Width (mm) Depth (mm) (mm) (mm) 1 8 8 2 0.1 0.03 2 8 8 100.4 0.1 3 8 30 2 0.2 0.1 4 8 30 10 0.4 0.1 5 30 8 5 0.4 0.1 6 30 8 20 10.2 7 30 30 5 0.4 0.1 8 30 30 20 1 0.2 9 450 30 5 0.4 0.1 10 450 30 20 10.2 11 450 30 60 2 0.5 12 450 270 45 2 0.5 13 450 270 20 1 0.2 14 450270 60 3 1 15 450 2000 20 2 0.5 16 450 2000 45 1 0.2 17 450 2000 60 3 118 2000 2000 60 3 1 19 2000 2000 100 10 10 20 2000 7000 60 3 1 21 20007000 100 10 10 22 7000 2000 60 3 1 23 7000 2000 100 10 10 24 7000 700060 3 1 25 7000 7000 100 30 30

Example 5

15.1 g of leuprorelin acetate was dissolved in 15.0 g of distilled waterunder warming. To this solution, 323.6 g of a separately prepareddichloromethane solution of a lactic acid-glycolic acid copolymer(hereinafter referred to as PLGA) [lactic acid/glycolic acid=75/25(molt), weight-average molecular weight 10,500] (121 g of PLGAcontained) was added, followed by emulsification with stirring using amini-mixer for 2 minutes (rotation rate 10,000 rpm; temperature of themixture: 40° C. or below). This emulsion was cooled to 18° C. to 19° C.and added to 25 l of a previously prepared 0.1% aqueous solution ofpolyvinyl alcohol (PVA) (18% to 19%), followed by emulsification again.While this W/O/W emulsion was gently stirred, the solvent was removedover a period of about 3 hours. The MCs obtained were passed through a75 μm sieve to remove coarse particles, after which they were subjectedto wet sieving through sieves of 90 μm pore size in the presence of asmall amount of distilled water. 18.4 g of D-mannitol was added to theproduct suspension and dissolved to yield a MC suspension.

In a freeze-drying tray (width 170 mm, length 260 mm, depth 40 mm), anice layer about 2 mm in thickness is formed with water for injection at−30° C. 400 ml of a MC suspension as mentioned above is added onto thefreeze-drying tray with the ice layer, and thoroughly frozen at about−30° C., followed by freeze-drying by a conventional method or a methoddescribed in the following Example 7.

The freeze-dried specimen obtained by this method, is easily recoveredfrom the tray, with no MC powder adhesion on the tray surface.

Example 6

15.1 g of leuprorelin acetate was dissolved in 13.0 g of distilled waterunder warming. To this solution, 323.6 g of a separately prepareddichloromethane solution of a lactic acid-glycolic acid copolymer(hereinafter referred to as PLGA) [lactic acid/glycolic acid=75/25 (mol%), weight-average molecular weight 10,500] (121 g of PLGA contained)was added, followed by emulsification with stirring using a mini-mixerfor 2 minutes (rotation rate 10,000 rpm; temperature of the mixture: 40°C. or below).

This emulsion was cooled to 18° C. to 19° C. and added to 25 l of apreviously prepared 0.1% aqueous solution of polyvinyl alcohol (PVA)(18° C. to 19%), followed by emulsification again. While this W/O/Wemulsion was gently stirred, the solvent was removed over a period ofabout 3 hours. The MCs obtained were passed through a 75 μm sieve toremove coarse particles, after which they were subjected to wet sievingthrough sieves of 90 μm pore size in the presence of a small amount ofdistilled water. 18.4 g of D-mannitol was added to the productsuspension and dissolved to yield a MC suspension.

In a freeze-drying tray (width 170 mm, length 260 mm, depth 40 mm), anice layer about 2 mm in thickness is formed with water for injection at−30° C. 400 ml of the MC suspension as mentioned above is added onto thefreeze-drying tray with the ice layer, and thoroughly frozen at about−30° C., followed by freeze-drying by a conventional method described inExample 7.

The freeze-dried specimen obtained by this method, is easily recoveredfrom the tray, with no MC powder adhesion on the tray surface.

Example 7 Application to Sustained-Release MC (1-Month Preparation)Suspension

In a freeze-drying tray (width 170 mm, length 260 mm, depth 40 mm), anice layer about 2 mm in thickness was formed with water for injection at−30° C. An ice layer was also formed on the inner wall of the tray (icelining). 200 mL of the MC suspension as obtained in Reference Example 1above, previously cooled to about 5° C., was added onto thefreeze-drying tray with ice layer, and thoroughly frozen at about −30°C., followed by freeze-drying by a following method.

After the MC suspension was frozen, the temperatures of the shelves inthe freeze-drying apparatus was raised up to −5° C. at a rate of 20°C./hr, then the temperatures were kept around −5° C. for about 20 hours.After the ice was sublimated, the temperatures of the shelves wereraised up to 51° C. at a rate of 20° C./hr, then kept the temperaturesaround 51° C. for about 48 hours.

After freeze drying, the appearance of the freeze-dried cake of MCs andthe status of detaching/recovery of the freeze-dried cake of MCstherefrom were observed.

Crumbling of the cake of the freeze-dried MCs, and also dispersing andscattering of the MCs out of the tray were not observed. The cake of thefreeze-dried MCs is easily recovered from the tray, with no MC powderadhesion on the tray.

Example 8 Application to Sustained-Release MC (3-Month Preparation)Suspension

In a freeze-drying tray (width 170 mm, length 260 mm, depth 40 mm), anice layer about 2 mm in thickness is formed with water for injection at−30° C. An ice layer is also formed on the inner wall of the tray (icelining). 200 mL of the MC suspension as obtained in Reference Example 2above, previously cooled to about 5° C., is added onto the freeze-dryingtray with ice layer, and thoroughly frozen at about −30° C., follows byfreeze-drying by a following method.

After the MC suspension is frozen, the temperatures of the shelves inthe freeze-drying apparatus are raised up to −5° C. at a rate of 20°C./hr, then the temperatures were kept around −5° C. for about 20 hours.After the ice is sublimated, the temperatures of the shelves are raisedup to 51° C. at a rate of 20° C./hr, then the temperatures are keptaround 51° C. for about 48 hours.

Crumbling of the cake of the freeze-dried MCs, and also dispersing andscattering of the MCs out of the tray are not observed. The cake of thefreeze-dried MCs is easily recovered from the tray, with no MC powderadhesion on the tray.

Industrial Applicability

According to the production method of the present invention, therecovery rate of solid sustained-release preparations is markedlyimproved, because there is no adhesion of the freeze-drying containerand solid sustained-release preparation so that the solidsustained-release preparation can be recovered without scraping.Furthermore, because of the short environmental exposure time, sterilityretention for the solid sustained-release preparation is improved. Inaddition, by using the production method of the present invention whichcomprising completing the sublimation of frozen water in thefreeze-drying container under a reduced condition that the temperaturesin the freeze-drying container is 0° C. or below, the collapsing of thefreeze-drying cake is prevented, the scattering of the MC powder isprevented and the freeze-dried MC powder can be recovered unexpectedlyin a good form and high yield.

1. A method for producing a solid sustained-release preparation, whichcomprises freeze-drying a sustained-release preparation in afreeze-drying container of which the inner face is partially or whollycoated with an ice layer or water-repelling base material: wherein theice layer has a thickness of about 0.1 mm to about 30 mm; and whereinthe water-repelling base material is ethylene tetrafluoride resin,ethylene trifluoride resin, ethylene difluoride resin, vinylidenefluoride resin, propylene hexafluoride-ethylene tetrafluoride copolymerresin, modified fluorine resin, ethylenetetrafluoride-perfluoroalkoxyethylene copolymer resin, or ethylenetetrafluoride-ethylene copolymer resin.
 2. A method for producing asolid sustained-release preparation, which comprises freeze-drying asustained-release preparation in a freeze-drying container of which theinner face is partially or wholly coated with a water-repelling basematerial, and the coated inner face is further partially or whollycoated with an ice layer.
 3. The method according to claim 1 wherein theinner face is the bottom face alone.
 4. The method according to claim 1wherein the freeze-drying container is a tray. 5-6. (canceled)
 7. Themethod according to claim 1 wherein said sustained-release preparationis a microsphere.
 8. The method according to claim 1 which comprisescompleting the sublimation of frozen water in the freeze-dryingcontainer under reduced condition that the temperature in thefreeze-drying container is 0° C. or below.
 9. The method according toclaim 3 wherein said sustained-release preparation is a microsphere. 10.The method according to claim 4 wherein said sustained-releasepreparation is a microsphere.
 11. The method according to claim 2wherein the inner face is the bottom face alone.
 12. The methodaccording to claim 2 wherein the freeze-drying container is a tray. 13.The method according to claim 2 wherein said sustained-releasepreparation is a microsphere.
 14. The method according to claim 2 whichcomprises completing the sublimation of frozen water in thefreeze-drying container under reduced condition that the temperature inthe freeze-drying container is 0° C. or below.